8 Proceedings of the Royal Society of Victoria. 



Reduction of the Observations. 



This was done in the manner (now well-known) adopted at 

 Greenwich, Kew, and Melbourne. The method of reduction can 

 be easily understood with the aid of the following notation : — 



/= duration of a set of swings. 



n — number of coincidences in a set. 



iV= interval between two consecutive coincidences. 



]Vo = approximate value of jY. 



R = number of siderial seconds in a solar day increased by the 

 rate of the Shelton clock = 86636 '56 + rate. 



j9 — mean barometric pressure (corrected). 



7'= mean temperature (corrected). 



a, ^ = initial and final amplitudes in inches. 



D, d, ?- = distances of arc scale from the telescope, tail-piece 

 and knife-edge respectively measured in inches. 



y= vibration number. 



Vo = approximate value of V. 



I is obtained by subtracting the epochs of the first three from 

 those of the last three coincidences and taking the mean of the 

 difterences : No is observed directly during the experiments, and ti 

 is obtained by dividing No into /, being the nearest whole number 



to the quotient : - then gives N. 



Pressure correction = Q-2,A: , q.qa.>3 ,j-_ oo \ = /?• 



Arc correction = Vo.— ^ \ nA-ZZ-^n-/?' \ 



\<orD- \ ^ •' i 



-0-13 \ -^^ _x a_b i =«• 



Temperature correction = 0.45 (7^-62) = r 



.-. F = ^-^+a-f/3 + T. 



N 



The reduction is to standard temperature 62°F., and standard 

 pressure 26 inches of mercury. 



The results are given in Table III. 



* Tlie coeflRcient 0'13 is Ciilculateil from tlie following appro.timate values :— Z>^71, ;— 50, 

 d— 1, Ko-seouo. 



